1. Field of the Invention
The present invention relates generally to polyurea elastomers and, more specifically, to spray and reaction injection molded polyurea elastomer systems which employ novel chain extenders.
2. Description of Background Art
Elastomer systems are commonly recognized as, among other things, coating materials, with spray polyurea elastomer systems being particularly useful when employed in this capacity. Spray polyurea elastomers are also employed in other open mold spraying applications for part production. Polyurea elastomers are also used for part production in closed mold applications, such as reaction injection molding (RIM) and reinforced reaction injection molding (RRIM). In addition, polyurea elastomers can be used in small mold filling type work, such as electric potting work.
Polyurea elastomer systems are generally prepared by reacting an isocyanate with an active hydrogen component in the presence of a chain extender. One of the problems confronting the skilled artisan is the difficulty of incorporating the chain extender into the polyurea elastomer system. More particularly, solid chain extenders are oftentimes difficult to process. Therefore, the availability of a liquid chain extender which is easily processed would be a significant contribution to the art.
U.S. Pat. No. 3,979,364 describes the use of aminated polyethers as hereinafter used as a component with a polyol to make an elastomer.
U.S. Pat. No. 3,666,788 describes the use of cyanoalkylated aminated polyethers in spray systems.
U.S. Pat. Nos. 4,379,729; 4,444,910, and 4,433,067 describe elastomers which are prepared using a high molecular weight amine terminated polyether, an aromatic diamine chain extender and an aromatic polyisocyanate which may merely be a polyisocyanate or a quasi-prepolymer prepared from a polyol reacted with a polyisocyanate wherein some isocyanate groups are still left unreacted. Various patents have been applied for and received using the basic combination recited above, as well as various mold release agents and other additives, such as catalysts and fillers, including glass fibers; for example, see U.S. Pat. No. 4,607,090.
U.S. Pat. No. 3,714,128 describes cyanoalkylated polyoxyalkylene polyamines which are useful for slowing the gelling or hardening of the polyurea component so that good mixing of the isocyanate and amine components can be attained, which gives the sprayed material ample time to adhere and level before gelation of the polyurea coating occurs. This patent does not describe the particular chain extenders employed in the elastomer of the present invention.
U.S. Pat. No. 4,806,615 describes reaction injection molded elastomers consisting of a cured reaction product of primary or secondary amine terminated polyethers of greater than 1500 molecular weight, an aromatic polyisocyanate, a combination of an unsubstituted aromatic diamine chain extender, and a substituted acyclic aliphatic diamine chain extender.
U.S. Pat. No. 4,218,543 describes the use of high molecular weight polyols, certain aromatic diamines and isocyanates for the production of RIM parts. This patent specifically claims as a chain extender 1-methyl-3,5-diethyl-2,4-diaminobenzene (diethyltoluenediamine) and its isomer.
U.S. Pat. No. 4,523,004 discloses a substituted aromatic diamine chain extender in a RIM product.
U.S. Pat. No. 4,631,298 discloses blending various slower reacting chain extenders with diethyltoluenediamine in a RIM system using amine terminated polyethers.
U.S. Pat. No. 4,585,850 describes a reaction injection molded elastomer made by reacting, in a closed mold, an amine terminated polyether of greater than 1500 average molecular weight, having greater than 50 percent of their active hydrogens in the form of amine hydrogens; a chain extender; flaked glass pretreated with an amino silane coupling agent; and an aromatic polyisocyanate.
Thus, it is our understanding that a polyurea elastomer system which incorporates the particular chain extenders described hereinbelow and which overcomes those problems discussed above has heretofore been unavailable.